It is frequently necessary to close an opening in a tubular member either permanently or semi-permanently, that is, to close an opening where a valve is not required or is not desirable. One example of a semi-permanent closure arises when a hot tap is made into a pipeline or a vessel through a fitting connected to the pipeline or vessel. In the typical hot tapping application as utilized in the petroleum industry, a fitting usually in the form of a flange is welded on the exterior of a pipe that has flowing gas or liquid under pressure. A valve is then secured to the flange and a hot tapping machine secured to the valve. By use of highly specialized equipment, a hole can then be drilled through the wall of the pipe while a gas or liquid continues to flow through it to provide access to the interior of the pipe, such as for inserting equipment to temporarily block flow through the pipe while repairs are being made. After the repairs are complete the equipment is removed but the opening that provides communication to the interior of the pipe needs to be closed. Preferably the closure is made in such a way that at some future date access can be again obtained through the fitting to the interior of the pipe. This is just one example of the need for a closure for an opening in a tubular member.
For background information relating to closure devices, reference may be had to the following United States patents:
U.S. PAT. NO. INVENTOR TITLE 2,010,200 Reufener et al. Sealing Device for Pressure Containers 2,281,145 Duey Pipe Plug 2,287,750 Clayton Fill Pipe Cap 2,431,778 Sosaya Test Cap 2,512,041 Steele Temporary Drainpipe Closure 3,114,528 Forest Base and Lock Assembly for Pipe 3,155,116 Ver Nooy Apparatus for Closing Side Openings into Pipelines 3,179,446 Paterson Extension Fitting Having Initial Flexible Lip Seal Gasket 3,483,894 Finocchiaro High Pressure Pipe Test Plug 3,765,456 Karpenko Chemical Cleaning Line Connector 3,766,947 Osburn Fluid Tight Closure 4,377,185 Katz Hydrotest Apparatus 4,387,740 Vanzant Cam-Flange 4,466,550 Sullivan Closure for a Cylindrical Opening Having Improved Venting Means 4,576,778 Ferree et al. Core Barrel Plug 4,609,209 Ralls Precise Alignment Adapter Flange 4,693,278 Wilson et al. Safety Closure Member 4,902,043 Zillig et al. Fluid Coupling and Seal Assembly 5,035,266 Benson et at. Mechanical Plug for Clean- Out Tees 5,038,830 Arnaud Pipe and Sealing Device 5,437,309 Timmons Lockable Well Cap 5,450,765 Stover Apparatus for Providing Signal Communication Between the Interior and Exterior of a Pipeline 5,975,142 Wilson Removable Closure System